1. Field Of Invention The invention relates to plastic molding equipment and more particularly to injection port shutoff devices and methods.
2. Related Art
The conventional way of shutting off injection molding gates is by a gate that moves transversely across the gate opening. In some injection molding devices the shutoff is at the sprue end and in others there is a cold runner which runs from the end of the sprue to the mold gate and the shutoff is transverse to that cold runner. A few of the molding devices which have the shutoff at the end of the sprue use an oblique shutoff than goes into the gate to end up substantially flush with the inner surface of the mold wall, thus minimizing the amount of extra material left on the molded part. However, since the sprue is typically heated, this is hot molten plastic and will thus leave a mold flashing in the region of the clearance between the gate and the gate port. With the cold runner shutoffs, there is typically a tab left. These tabs and flashings are ubiquitous in molded plastic parts despite their recognized undesirability.